Synthesis and electrochemical performance of modified LiMn2O4 by Zn2 + and PO43 − co-substitution

The cathode-active materials LiMn2O4LiZn0.05Mn1.95O4(PO4)x (x = 0, 0.025, 0.05) were synthesized via traditional solid state reaction. Ball milling technique and citric acid additive were employed to obtain the as-prepared products with nanoscaled particles, which were characterized by various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and charge–discharge studies. Doping the Mn spinel with Zn2 + ions can increase the overall Mn oxidation state and minimize Jahn–Teller distortion. It is shown that LiZn0.05Mn1.95O3.96(PO4)0.025 and LiZn0.05Mn1.95O3.99 samples have almost identical discharge capacities of about 114 mAh·g− 1 in the first cycle and the capacity retention rate of LiZn0.05Mn1.95O3.96(PO4)0.025 is superior to that of LiZn0.05Mn1.95O3.99 and the undoped LiMn2O4. The results demonstrate that doped zinc and phosphate can stabilize the structural integrity of the spinel host by suppressing the Jahn–Teller distortion and also provide short distance for Li+ diffusion upon cycling.